The Lüliang Massif: a key area for the understanding of the Palaeoproterozoic Trans-North China Belt, North China Craton
Abstract
This paper documents the first detailed structural analysis of the Lüliang Massif in the Trans-North China Belt, North China Craton. A nappe, made up of a Terrigeneous and Mafic Unit (TMU) derived from an oceanic basin thrust over gneisses and volcanic-sedimentary rocks, is interpreted as a magmatic arc deposited upon a TTG basement. The nappe is rooted to the west in the Trans-North China Suture that separates the Fuping Block from the Western Block. Nappe stacking, coeval with a top-to-the-SE synmetamorphic D1 event, is dated around 1890–1870 Ma using chemical U–Th/Pb EPMA datings on monazite and U–Pb LA-ICP-MS dating on zircon. A second D2 ductile event, characterized by SE-verging folds, reworks the D1 structures. D2 is the first event recorded in the late-orogenic sedimentary series that unconformably covers the metamorphic units formed during D1. These lithological, structural and geochronological results are correlated with those described in the eastern massifs of Hengshan, Wutaishan and Fuping. The Trans-North China Belt resulted from the collision of the Fuping Block and the Western Block after a westward-directed subduction and subsequent closure of an oceanic basin where the TMU was deposited.